Just got my 74 big block running and it's been starting fine but it only wants to run smooth and good when the choke Is full on but when taken off it runs like a dog and backfires out the tailpipe haven't been able to time it seems to run like its a tooth off timing but its right on tdc. Any help or advice I'd appreciate it

I'd start by looking for a vacuum leak...anywhere from a power brake booster to a vacuum line, a pcv hose, carb base gaskets and intake to head gaskets to the carb itself. If it runs better when you close the choke, there's too much air gettin' in there somewhere.

Carb probably , I just had my 472 which always started good , and last three times starting it , it would backfire through the exhaust bad until it warmed up, I finally noticed a slow seeping leak from the rear metering block when cold, not enough to see a drip but wet if you ran your finger across it. Tried another carb and it was fine , I figured it was the old plugs until I noticed the small leak.